update-submodules.yml

# Nightly job that bumps every git submodule to the latest upstream HEAD
# and opens (or updates) a PR so the change goes through normal review.
name: Update submodules

on:
  schedule:
    # 03:00 UTC every day
    - cron: "0 3 * * *"
  workflow_dispatch:

permissions:
  contents: write
  pull-requests: write

jobs:
  update:
    name: Bump submodules to latest HEAD
    runs-on: ubuntu-latest

    steps:
      - name: Checkout (no submodules)
        uses: actions/checkout@v4
        with:
          submodules: false

      - name: Update every submodule to remote HEAD
        id: update
        shell: bash
        run: |
          git submodule sync
          git submodule update --init --remote --depth 1

          if git diff --quiet HEAD; then
            echo "changed=false" >> "$GITHUB_OUTPUT"
          else
            echo "changed=true" >> "$GITHUB_OUTPUT"
          fi

      - name: Commit and push if changed
        if: steps.update.outputs.changed == 'true'
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"
      
          git add .
          git commit -m "chore: update submodules to latest HEAD"
          git push origin HEAD:main